X-ray tubes can include a target material for production of x-rays in response to impinging electrons from an electron emitter. It can be advantageous to have multiple target regions, and the ability to selectively direct the electron beam to each region. For example, a new region of the target can be used when a previously used region has worn out or become too pitted for further use. Another advantage is selecting x-ray energy spectra emitted from different target materials in different target regions. For example, if the target includes a silver region and a gold region, x-rays emitted when the electron beam is directed at the silver region will have a different energy spectra than x-rays emitted when the electron beam is directed at the gold region.
Redirecting the electron beam to different regions of the target can be undesirable due to a different resulting direction or location of emitted x-rays. If x-rays are emitted in one direction while using one region of the anode, then emitted in another direction while using another region of the anode, the x-ray user may need to re-collimate and/or realign the x-ray tube with each different use. This need to re-collimate or realign optics can be undesirable.
Information relevant to attempts to address these problems can be found in U.S. Pat. Nos. 3,753,020, 2,298,335, 2,549,614, 6,560,315, 3,900,751, 7,973,394, and 5,655,000; U.S. Patent Publication Number US 2011/0135066; and Japan Patent Number JP 3,812,165.